Regulating Twitter is little different than regulating say billboards: https://www.cga.ct.gov/2006/rpt/2006-R-0553.htm

Public airwaves (TV, radio) have have fines for breaking various rules even when it’s a member of the public speaking live. Thus the classic tape delay and bleeps on all life content.

Further back Newspapers, advertising, and letters to the editor etc where limited for so long that it was a constitutional issue in 1776.

So having platforms is hardly a new thing. We have been debating such freedoms for so long it’s part of various countries cultural identity.